The field of the invention is waste recycling.
The amount of waste in the world is a big problem, and contributing significantly to the problem are wastes that are created as by-products of industrial processes. Methods for disposing of these wastes are often expensive and environmentally disfavored, particularly when the waste is hazardous. Disposal of hazardous waste is expensive, at least in part because special care in shipping and collection is required, specially designed storage tanks may be necessary, and hazardous wastes are disposed of in specifically permitted facilities. While it may be less expensive to dispose of non-hazardous waste, the concept of disposal is not favored because of its negative environmental impact.
In order to solve some of the above-enumerated problems, waste products may be recycled. Of course, recycling eliminates the cost of disposal to the extent that the waste is used, but recycling may turn out to be more expensive than disposal, because of the expenses to accumulate, pack, and ship the waste products. This is particularly true with respect to finely ground or particulate waste which is especially difficult to accumulate, pack, and use in another product. Additionally, finding entities to purchase some types of waste as well as some waste derived recycled products may prove to be difficult and time consuming, because of lack of demand for the product. Often times it is easier, albeit less favored, to simply dispose of the waste. Therefore, it is important to find additional financially feasible uses for waste products and waste-derived recycled products.
A use for recycled waste paint is disclosed in U.S. Pat. No. 5,496,404 to Price and Long (March 1996). The ""404 patent teaches that waste paint can be used in the manufacture of Portland cement. The waste paint is added to the process after burning the raw materials. During the burning process, the raw materials become chemically attached and partially fused forming lumps of cement clinker. These lumps are usually finely ground to form Portland cement, and it is during this grinding step that the ""404 patent contemplates addition of the waste materials. In this case, the mineral content of the waste may provide benefit to the Portland cement. A limitation with respect to adding the waste during the grinding is that only a small number of materials are usable at this point. The usable materials are generally limited to high calcium/low silica materials.
Another use for waste materials in the manufacture of Portland cement involves using high fuel value wastes to contribute heat to the burning process. During the manufacturing process for Portland cement, raw materials are usually burned within a kiln. The burning process may be calcining, roasting, autoclaving or some other process, but in any case, the process is generally performed at about 2600 degrees Fahrenheit. U.S. Pat. No. 4,081,285 to Pennel (March 1978) teaches that high fuel value waste such as oil based paint may be burned outside of the kiln as an aid to reaching the required temperature. Still, there is a need to find other uses for wastes, especially those that do not contribute significant fuel value.
One such use is as an agglomerating agent to bond particulates. U.S. Pat. No. 6,162,164 to Long and Segala (December 2000) addresses the expenses and issues associated with the handling and use of particulates. Particulates are those materials that have very small particles. For example, fly ash, cinder fines, shale fines, and fine silica sand. While these products may have value in the production of other products, recycling them was often not feasible because of the cost involved in handling, packing, and using them. The ""164 patent teaches agglomeration. It is presumably much easier to manage the agglomerated product, and therefore the costs of handling, packing, and using the waste is reduced. However, problems related to finding uses for the agglomerated material remain.
Thus, there is a long-standing need to find cost effective uses for agglomerated low fuel value waste material, particularly in Portland cement.
The present invention provides methods and systems of incorporating a mineral based particulate into Portland cement. The method and systems include agglomerating a particulate material and an agglomerating material to produce an additive. The additive is introduced into a kiln before burning. By introducing the additive before burning, minerals may be added to cement clinker.
Various objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments of the invention, along with the accompanying drawings in which like numerals represent like components.